1. Field of the Invention
This invention relates to thread chain back-tackers for overlock sewing machines and, more particularly, to a thread chain back-tacker for an overlock sewing machine which can eliminate defective back-tacking of surplus thread chain having been cut from a cloth at a former position, to the start end of a cloth at a subsequent position, permitting satisfactory back-tacking at all times.
2. Description of the Related Art
To prevent loosening of the tacking start portion of a cloth, various back-tacking machines have been proposed in which a free thread chain surplus separated from the cloth at a former position thereof is back-tacked to a tacking start seam of the cloth at a subsequent position.
In the prior art thread chain back-tacker, the cloth end curls at the beginning of the back-tacking. In avoiding this drawback, the thread chain is caused to project from the cloth end at the start of back-tacking or loosening of upper looper yarn tension, thus resulting in defective back-tacking; that is, satisfactory results of back-tacking fail to be obtained.